Fair Value Measurements (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended		0 Months Ended				12 Months Ended		12 Months Ended
	Dec. 31, 2013	Jun. 14, 2013	Jun. 14, 2013 Senior Redeemable Preferred Stock [Member]	Aug. 24, 2012 Senior Redeemable Preferred Stock [Member]	May 16, 2012 Senior Redeemable Preferred Stock [Member]	Apr. 08, 2011 Senior Redeemable Preferred Stock [Member]	Dec. 31, 2013 Senior Redeemable Preferred Stock [Member]	Dec. 31, 2011 Senior Redeemable Preferred Stock [Member]	Dec. 31, 2013 Public Preferred Stock [Member]	Dec. 31, 2012 Public Preferred Stock [Member]	Dec. 31, 1991 Public Preferred Stock [Member]	Dec. 31, 1990 Public Preferred Stock [Member]	Dec. 31, 2013 Estimate of Fair Value, Fair Value Disclosure [Member] Public Preferred Stock [Member]	Dec. 31, 2012 Estimate of Fair Value, Fair Value Disclosure [Member] Public Preferred Stock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Redemption price of senior preferred stock			$ 2.0	$ 2.0	$ 2.0	$ 2.1
Percentage of stock redeemed (in hundredths)		54.50%		36.00%	26.70%	22.30%
Carrying amount of senior redeemable preferred stock							1.9	4.0
Preferred stock dividend rate per annum (in hundredths)	12.00%						14.125%		12.00%	12.00%	6.00%	6.00%
Public preferred stock par value (in dollar per share)									$ 0.01
Public preferred stock													48.9	47.8
Carrying value of public preferred stock									$ 116.3	$ 112.5